1. Field of the Invention
The invention relates to a roll.
2. Description of the Prior Art
Installations for the continuous casting of steel employ split rolls to support the continuously cast strands formed in the installations. Each split roll is made up of several roll segments which are arranged side-by-side. The roll segments have necks which are journalled in bearing assemblies, and each roll segment is provided with an axial channel for a cooling medium. The channels of the various roll segments are aligned, and a cooling medium inlet is located at one end of the roll while a cooling medium outlet is located at the other end of the roll.
One type of split roll has separate roll segments with the neighboring necks of two roll segments supported by individual bearing assemblies. Each bearing assembly is held on the respective neck by an end plate which is fixed to the corresponding roll segment by screws. The end plates include sealing arrangements for the respective cooling channels.
In a split roll of this type, there are two end plates between adjoining roll segments. Consequently, the portions of the roll segments which support a continuously cast strand are separated by a relatively large gap in which the strand is unsupported. Since continuously cast steel strands have very high temperatures, the strands tend to bulge considerably when unsupported over large distances. This is not only bad for strand quality but also leads to problems in subsequent processing.
Another type of split roll has one-piece roll segments with neighboring segments sharing a common neck journalled in a common bearing assembly. To allow the bearing assembly to be placed around the neck, the entire bearing assembly is divided. This includes the seals of the bearing assembly, the inner and outer races of the bearing proper, and the housing for the bearing proper.
A significant amount of room is required to install a bearing assembly of this kind. Accordingly, a large gap once again exists between the portions of the roll segments which support a continuously cast strand.
As mentioned above, each roll segment is provided with an axial channel for a cooling medium. A connecting tube bridges the cooling channels of two adjoining roll segments. The cooling channels are bounded by internal surfaces of the roll segments, and these surfaces form sealing surfaces which contact the tube. With this arrangement, it is necessary to remachine or replace a roll segment when the sealing surface becomes worn or damaged. Remachining is time-consuming and constitutes an expense while replacement of a roll segment is very costly.
The bearing in a conventional split roll has an axial extension which lies between the neck of an associated roll segment and the housing for the bearing. The extension has a sealing surface which bears against a mating surface of the housing and another surface which bears against the neck. If either surface becomes worn or damaged, the bearing must be remachined or replaced at considerable expense.
Furthermore, in a conventional split roll, the inner races of the bearings are fixed against axial displacement while the outer races float to allow for thermal expansion. Fixing of the inner races is accomplished by abutting the inner races against shoulders on the corresponding roll segments. This requires very accurate machining which is time-consuming and costly.
As noted previously, continuously cast steel strands have very high temperatures. Based on this consideration, the housing of a bearing assembly is constructed from a material, or a combination of materials, providing heat resistance and efficient heat removal. The same material or combination of materials is used throughout the housing. Since heat-resistant materials with good heat transfer characteristics are costly, the use of such materials for the entire housing represents a considerable expense.